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| 1 | +/// Create BTree. |
| 2 | +use crate::*; |
| 3 | + |
| 4 | +#[derive(Debug, Clone, PartialEq)] |
| 5 | +pub struct BTreeNode { |
| 6 | + pub page: Page, |
| 7 | + pub page_num: usize, |
| 8 | + pub children: Option<Vec<BTreeNode>>, |
| 9 | + pub overflow: Option<Vec<OverflowNode>>, |
| 10 | +} |
| 11 | + |
| 12 | +#[derive(Debug, Clone, PartialEq)] |
| 13 | +pub struct OverflowNode { |
| 14 | + pub page: OverflowPage, |
| 15 | + pub page_num: usize, |
| 16 | +} |
| 17 | + |
| 18 | +impl BTreeNode { |
| 19 | + pub fn new(page_num: usize, reader: &Reader) -> Result<Self, StdError> { |
| 20 | + let page = reader.get_btree_page(page_num)?; |
| 21 | + let mut children = vec![]; |
| 22 | + let mut overflow = vec![]; |
| 23 | + |
| 24 | + let mut extend_overflow = |cell_overflow: &Option<CellOverflow>| { |
| 25 | + if let Some(o) = cell_overflow { |
| 26 | + let res = Self::follow_overflow(vec![], o.units.to_vec(), o.page as usize, reader); |
| 27 | + if let Ok(res) = res { |
| 28 | + let mut page_nums = |
| 29 | + res.iter().map(|o| o.next_page as usize).collect::<Vec<_>>(); |
| 30 | + |
| 31 | + // Transform list of 'next_page' numbers into page numbers. |
| 32 | + // Last next page number is 0 to mark the end of the linked list. |
| 33 | + page_nums.insert(0, o.page as usize); |
| 34 | + page_nums.pop(); |
| 35 | + |
| 36 | + let overflow_list = res |
| 37 | + .into_iter() |
| 38 | + .zip(page_nums.into_iter()) |
| 39 | + .map(|(o, n)| OverflowNode { |
| 40 | + page: o, |
| 41 | + page_num: n, |
| 42 | + }) |
| 43 | + .collect::<Vec<OverflowNode>>(); |
| 44 | + overflow.extend(overflow_list); |
| 45 | + } |
| 46 | + } |
| 47 | + }; |
| 48 | + |
| 49 | + for outer_cell in page.cells.iter() { |
| 50 | + match outer_cell { |
| 51 | + Cell::TableInterior(cell) => { |
| 52 | + children.push(BTreeNode::new(cell.left_page_number as usize, reader)?); |
| 53 | + } |
| 54 | + Cell::TableLeaf(cell) => { |
| 55 | + extend_overflow(&cell.overflow); |
| 56 | + } |
| 57 | + Cell::IndexInterior(cell) => { |
| 58 | + children.push(BTreeNode::new(cell.left_page_number as usize, reader)?); |
| 59 | + extend_overflow(&cell.overflow); |
| 60 | + } |
| 61 | + Cell::IndexLeaf(cell) => { |
| 62 | + extend_overflow(&cell.overflow); |
| 63 | + } |
| 64 | + }; |
| 65 | + } |
| 66 | + if page.page_header.page_type.is_interior() { |
| 67 | + // Don't forget the right-most pointer, which is in the page header. |
| 68 | + // If it's interior page, then page_num is Some by design. |
| 69 | + children.push(BTreeNode::new( |
| 70 | + page.page_header.page_num.unwrap() as usize, |
| 71 | + reader, |
| 72 | + )?); |
| 73 | + }; |
| 74 | + |
| 75 | + Ok(Self { |
| 76 | + page, |
| 77 | + page_num, |
| 78 | + children: (!children.is_empty()).then_some(children), |
| 79 | + overflow: (!overflow.is_empty()).then_some(overflow), |
| 80 | + }) |
| 81 | + } |
| 82 | + |
| 83 | + fn follow_overflow( |
| 84 | + mut opages: Vec<OverflowPage>, |
| 85 | + overflow_units: Vec<OverflowUnit>, |
| 86 | + next_page: usize, |
| 87 | + reader: &Reader, |
| 88 | + ) -> Result<Vec<OverflowPage>, StdError> { |
| 89 | + let opage = reader.get_overflow_page(overflow_units, next_page)?; |
| 90 | + let units = opage.overflow_units.to_vec(); |
| 91 | + let next_page = opage.next_page; |
| 92 | + opages.push(opage); |
| 93 | + match next_page { |
| 94 | + 0 => Ok(opages), |
| 95 | + n => Self::follow_overflow(opages, units, n as usize, reader), |
| 96 | + } |
| 97 | + } |
| 98 | +} |
| 99 | + |
| 100 | +#[derive(Debug, Clone, PartialEq)] |
| 101 | +pub struct BTree { |
| 102 | + pub ttype: String, |
| 103 | + pub name: String, |
| 104 | + pub root: BTreeNode, |
| 105 | +} |
| 106 | + |
| 107 | +#[derive(Debug, Clone, PartialEq)] |
| 108 | +pub enum Schema { |
| 109 | + Type = 0, |
| 110 | + Name = 1, |
| 111 | + TableName = 2, |
| 112 | + RootPage = 3, |
| 113 | + SQL = 4, |
| 114 | +} |
| 115 | + |
| 116 | +impl BTree { |
| 117 | + pub fn new(cell: &TableLeafCell, reader: &Reader) -> Result<Self, StdError> { |
| 118 | + match &cell.overflow { |
| 119 | + Some(overflow) => { |
| 120 | + let payload = Self::follow_overflow( |
| 121 | + cell.payload.values.to_vec(), |
| 122 | + overflow.units.to_vec(), |
| 123 | + overflow.page as usize, |
| 124 | + reader, |
| 125 | + )?; |
| 126 | + Self::parse_tree(&payload, reader) |
| 127 | + } |
| 128 | + None => Self::parse_tree(&cell.payload.values, reader), |
| 129 | + } |
| 130 | + } |
| 131 | + |
| 132 | + fn follow_overflow( |
| 133 | + mut payload: Vec<RecordValue>, |
| 134 | + overflow_units: Vec<OverflowUnit>, |
| 135 | + next_page: usize, |
| 136 | + reader: &Reader, |
| 137 | + ) -> Result<Vec<RecordValue>, StdError> { |
| 138 | + // We need to merge last of previous with the first of overflow value and |
| 139 | + // add values in between to payload. |
| 140 | + /* |
| 141 | + * Btree page Overflow page 1 Overflow page 2 |
| 142 | + * +-----------+ +----------------------------+ +----------+ |
| 143 | + * | field1 | -> | field1 | field2 | field3 | -> | field3 | |
| 144 | + * +-----------+ +----------------------------+ +----------+ |
| 145 | + * ↓ ↓ | ↓ ↓ |
| 146 | + * +----------------+ ↓ +---------------+ |
| 147 | + * merge as it is merge |
| 148 | + */ |
| 149 | + let opage = reader.get_overflow_page(overflow_units, next_page)?; |
| 150 | + |
| 151 | + let mut overflow = opage.data.to_vec(); |
| 152 | + let last_payload = payload.remove(payload.len() - 1); |
| 153 | + let first_overflow = overflow.remove(0); |
| 154 | + match last_payload.merge(first_overflow.value) { |
| 155 | + Some(value) => payload.push(value), |
| 156 | + None => unreachable!("Attempt to merge the unexpected Record types."), |
| 157 | + }; |
| 158 | + payload.extend(overflow.into_iter().map(|v| v.value)); |
| 159 | + |
| 160 | + match opage.next_page { |
| 161 | + 0 => Ok(payload), |
| 162 | + n => Self::follow_overflow(payload, opage.overflow_units, n as usize, reader), |
| 163 | + } |
| 164 | + } |
| 165 | + |
| 166 | + fn parse_tree(values: &[RecordValue], reader: &Reader) -> Result<Self, StdError> { |
| 167 | + let tname = match &values[Schema::Name as usize].value { |
| 168 | + RecordType::Text(v) => v.as_ref().map_or("", |vv| vv), |
| 169 | + _ => unreachable!("Unknown type for table schema name."), |
| 170 | + }; |
| 171 | + let ttype = match &values[Schema::Type as usize].value { |
| 172 | + RecordType::Text(v) => v.as_ref().map_or("", |vv| vv), |
| 173 | + _ => unreachable!("Unknown type for table schema type."), |
| 174 | + }; |
| 175 | + let tpage = match values[Schema::RootPage as usize].value { |
| 176 | + RecordType::I8(v) => v as usize, |
| 177 | + RecordType::I16(v) => v as usize, |
| 178 | + RecordType::I24(v) | RecordType::I32(v) => v as usize, |
| 179 | + RecordType::I48(v) | RecordType::I64(v) => v as usize, |
| 180 | + _ => unreachable!("Unknown type for table schema root page."), |
| 181 | + }; |
| 182 | + Ok(Self { |
| 183 | + ttype: ttype.to_string(), |
| 184 | + name: tname.to_string(), |
| 185 | + root: BTreeNode::new(tpage, reader)?, |
| 186 | + }) |
| 187 | + } |
| 188 | +} |
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